EP3687949A1 - Wasserblockierende systeme mit fasern, die mit flüssigen, strahlungshärtbaren harzzusammensetzungen beschichtet sind - Google Patents

Wasserblockierende systeme mit fasern, die mit flüssigen, strahlungshärtbaren harzzusammensetzungen beschichtet sind

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Publication number
EP3687949A1
EP3687949A1 EP18807797.8A EP18807797A EP3687949A1 EP 3687949 A1 EP3687949 A1 EP 3687949A1 EP 18807797 A EP18807797 A EP 18807797A EP 3687949 A1 EP3687949 A1 EP 3687949A1
Authority
EP
European Patent Office
Prior art keywords
water
swellable
optical fiber
coated optical
coating
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Pending
Application number
EP18807797.8A
Other languages
English (en)
French (fr)
Inventor
Huimin Cao
Kangtai Ren
Mark Petrus Franciscus PEPELS
Johan Franz Gradus Antonius Jansen
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Covestro Netherlands BV
Original Assignee
DSM IP Assets BV
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Filing date
Publication date
Application filed by DSM IP Assets BV filed Critical DSM IP Assets BV
Publication of EP3687949A1 publication Critical patent/EP3687949A1/de
Pending legal-status Critical Current

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Classifications

    • C—CHEMISTRY; METALLURGY
    • C03—GLASS; MINERAL OR SLAG WOOL
    • C03C—CHEMICAL COMPOSITION OF GLASSES, GLAZES OR VITREOUS ENAMELS; SURFACE TREATMENT OF GLASS; SURFACE TREATMENT OF FIBRES OR FILAMENTS MADE FROM GLASS, MINERALS OR SLAGS; JOINING GLASS TO GLASS OR OTHER MATERIALS
    • C03C25/00—Surface treatment of fibres or filaments made from glass, minerals or slags
    • C03C25/10—Coating
    • C03C25/24—Coatings containing organic materials
    • C03C25/26—Macromolecular compounds or prepolymers
    • C03C25/28—Macromolecular compounds or prepolymers obtained by reactions involving only carbon-to-carbon unsaturated bonds
    • C03C25/285—Acrylic resins
    • C—CHEMISTRY; METALLURGY
    • C03—GLASS; MINERAL OR SLAG WOOL
    • C03C—CHEMICAL COMPOSITION OF GLASSES, GLAZES OR VITREOUS ENAMELS; SURFACE TREATMENT OF GLASS; SURFACE TREATMENT OF FIBRES OR FILAMENTS MADE FROM GLASS, MINERALS OR SLAGS; JOINING GLASS TO GLASS OR OTHER MATERIALS
    • C03C25/00—Surface treatment of fibres or filaments made from glass, minerals or slags
    • C03C25/10—Coating
    • C03C25/104—Coating to obtain optical fibres
    • C03C25/1065—Multiple coatings
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
    • G02B6/44—Mechanical structures for providing tensile strength and external protection for fibres, e.g. optical transmission cables
    • G02B6/4401—Optical cables
    • G02B6/4429—Means specially adapted for strengthening or protecting the cables
    • G02B6/44384—Means specially adapted for strengthening or protecting the cables the means comprising water blocking or hydrophobic materials

Definitions

  • the present invention relates to methods of coating water-blocking fibers, such as optical fibers, along with water-swellable compositions suitable for use therewith, the resulting water-blocking optical fibers, and buffer tubes incorporating such water-blocking optical fibers.
  • Optical fibers enable the guided transmission of light signals. They are preferable to alternative wire-based data-transmission media due to their ability to transmit data over longer distances without a significant loss in signal strength. Over the last several decades, an increased use of optical fibers has facilitated the global digital transformation. Thus, the telecommunication industry now utilizes optical fibers, especially those made from glass, as the preferred medium for data transmission.
  • surface coatings have long-since been applied to optical fibers for protection and to ensure a high-level of performance.
  • the surface coating compositions are typically applied to the glass fiber shortly after it has been drawn from the preform, preferably immediately after cooling. The coating compositions are then cured to produce the coated optical fiber.
  • optical fibers are frequently coated with two or more superposed radiation-curable coatings immediately after the fiber is produced by drawing.
  • the coating which directly contacts the optical fiber is called the “inner primary coating” and an overlaying coating is called the “outer primary coating.”
  • the inner primary coating has become more frequently referred to simply as the “primary coating”
  • the outer primary coating has become more frequently referred to simply as the “secondary coating.”
  • Primary coatings are typically formulated to possess a significantly lower modulus than secondary coatings.
  • the relatively soft primary coating provides resistance to microbending which results in added attenuation of the signal transmission (i.e. signal loss) of the coated optical fiber and is therefore undesirable.
  • Microbends are microscopic curvatures in the optical fiber involving local axial displacements of a few micrometers and spatial wavelengths of a few millimeters.
  • Microbends can be induced by thermal stresses and/or mechanical lateral forces. Coatings can provide lateral force protection that protect the optical fiber from microbending, but as coating thickness decreases the amount of protection provided decreases.
  • the harder outer Primary coating, that is, the Secondary coating provides resistance to handling forces such as those encountered when the coated fiber is ribboned and/or cabled.
  • Primary coatings preferably possess a higher refractive index than the cladding of the associated optical fiber, in order to allow them to strip errant optical signals away from the core of the optical fiber.
  • Primary coatings should maintain adequate adhesion to the glass fiber during thermal and hydrolytic aging, yet (if needed) be capable of being strippable therefrom for splicing purposes.
  • the primary coating typically has a thickness in the range of 20-50 ⁇ (e.g., about 25 or 32.5 ⁇ ), thinner thickness in the range of 15-25 ⁇ for 200 ⁇ fibers.
  • Secondary coatings contact and surround the primary coating.
  • the secondary coating is, for example, the polymerization product of a coating composition whose molecules have become highly crosslinked when polymerized.
  • the secondary coating has a high in-situ modulus (e.g., greater than about 800 MPa at 25 °C, more preferably between about 1 GPa to about 3 GPa) and a high T g (e.g., greater than about 50 °C).
  • the in-situ secondary modulus is preferably greater than about 1000 MPa.
  • Secondary coatings often possess a thickness that is less than about 40 ⁇ .
  • Fiber optic coatings including the primary and secondary layers, are applied using one of two processes: wet-on-wet (WOW) and wet-on-dry (WOD).
  • WOD wet-on-wet
  • the fiber passes first through a primary coating application, which is cured via exposure to electromagnetic (typically ultraviolet) radiation, then passes through a secondary coating application, which is subsequently cured by similar means.
  • the WOD process the fiber passes through both the primary and secondary coating applications prior to entering the curing step.
  • the curing lamps between primary and secondary coating application are therefore omitted.
  • UV lamps with broadband mercury spectra are commonly used in the industry, due to their high intensity and broad emission spectrum to ensure rapid and full cure of such radiation curable coatings.
  • UV-LED light emitting diodes
  • a plurality of optical fibers are grouped together (often linearly) by virtue of a ribbon.
  • Such optical fiber ribbons are comprised of a matrix material, which is typically UV-curable and may be formed from some of the same components which comprise the optical fiber primary and secondary coatings themselves.
  • several ribbons are stacked together and arranged in a substantially square or rectangular cross section to form what is known as a matrix.
  • the matrix is then inserted into a hollow, cylindrical protective sheath to form a so-called buffer tube. Because of the discrepancy in the cross-sectional shapes between the square (or rectangular) matrix and the circular buffer tube, a substantial unoccupied volume is created around the optical fiber matrix.
  • This interstitial space is often filled with a gel material, which further absorbs various impacts and stresses that might be applied to the optical fibers during downstream handling. Such gel also acts as a barrier to prevent water ingress into the optical fiber.
  • a group of coated optical fibers are inserted without a ribbon individually into the buffer tube, in some cases around a central strength member.
  • the buffer tubes in this instance may take the form of either a loose or tight configuration.
  • This void may be filled with a gel-type buffer tube filling material of the same variety used with matrix or ribbon configurations in order to serve substantially the same purpose.
  • a cable is ultimately manufactured by combining one or more buffer tubes with additional cable components, such as strength and protection members.
  • additional cable components such as strength and protection members.
  • multiple buffer tubes are bound together with strength members to establish a cable core.
  • the core may then be further protected by placing it within a core sheath.
  • This sheath may comprise multiple layers, each of which may be formed from either organic or inorganic materials to guard against a variety of potential ingressions to add further strength, in a manner which is well-known in the art.
  • a cable will be surrounded with a polymeric (such as polyethylene) upjacketing material to form an outer jacket to protect the cable from environmental exposure.
  • optical fibers are exposed to extreme temperature cycling, moisture, and water.
  • Optical fiber cables must be able to withstand such harsh conditions for many years or decades. Despite the foregoing protection measures, however, the challenge of sufficiently preventing moisture or water ingression remains in the industry.
  • the aforementioned tapes, yarns, or fibers mitigate the cleaning problems associated with gels, but their longitudinal water blocking performance may remain inferior, in part due to the heterogeneity of the coated or impregnated substrate.
  • powder- or particle-based solutions may cause environmental concerns and can contribute to reduced microbending performance of the coated optical fiber with which they are associated.
  • the relatively large required size and volume of the SAP -based or SAP -impregnated substrate (or even the particles themselves) used results in either a reduction in of the number of optical fibers which can be employed per given diameter buffer tube, or the utilization of larger-diameter buffer tubes. Either way, such solutions are ill-suited for applications requiring a high cable density (such as FTTX or metro applications).
  • the reference's lack of specificity about optimized SAP chemistry and its preference for SAP inclusion in such thick coating layers does not enable a coated optical fiber construction that would be optimally - or even sufficiently - longitudinally water-blocking.
  • a first embodiment is a water-swellable, radiation curable coating composition for an optical fiber including an acrylic acid, a salt of an acrylic acid, a monofunctional ethylenically unsaturated network former, a photoinitiator, a viscosity modifier, an amount of water, and a multifunctional crosslinker, wherein the water-swellable, radiation curable coating composition is a liquid at room temperature.
  • a second embodiment is an optical fiber coated with a primary coating, a secondary coating adhered to and surrounding the primary coating, and a water-swellable exterior coating adhered to and surrounding the secondary coating, wherein the water-swellable exterior coating is configured to buckle and detach from the secondary coating at least one point along a section of the coated optical fiber within 3 minutes after the coated optical fiber has been submerged in deionized water.
  • a third embodiment is a method of applying a liquid, water-swellable coating to a coated optical fiber comprising the steps of providing a coated optical fiber, applying a liquid water- swellable coating composition to an exterior surface of a section of coated optical fiber to form a coated optical fiber with a liquid water-swellable exterior coating composition, and exposing the coated optical fiber with the liquid water-swellable exterior coating composition to a light source capable of emitting ultraviolet radiation to affect curing of said liquid water-swellable exterior coating composition, to form a coated optical fiber with a water-swellable exterior coating, wherein the water-swellable exterior coating is configured to buckle and detach from the coated optical fiber at least one point along the section of the coated optical fiber within 3 minutes after the time from which the coated optical fiber with the water-swellable exterior coating has been submerged in deionized water.
  • a fourth embodiment is a buffered bundle of optical fibers, comprising a flexible buffer tube possessing a length and a cavity over at least a portion of the length, and a plurality of coated optical fibers disposed within the cavity of the flexible buffer tube along the portion, wherein at least one of the plurality of coated optical fibers comprises a water-swellable exterior coating, further wherein said water-swellable exterior coating is configured to buckle and detach from the coated optical fiber at least one point along a section thereof within 3 minutes from a time at which the cavity becomes filled with deionized water.
  • FIG. 1 is a cross-sectional view of a coated optical fiber according to an embodiment of the present invention.
  • FIG. 2 is a schematic of a test used herein to evaluate the relative longitudinal water- blocking performance of various coatings, coated optical fibers, and/or cable designs.
  • FIG. 3 a and FIG. 3b depict microscope images of an SAP-coated fiber according to the present invention with buckling and detaching behavior.
  • FIG.4 depicts a microscope image of an SAP-coated fiber that exhibits neither buckling nor detaching behavior.
  • FIG.5 depicts a microscope image of an SAP-coated fiber that has buckled but not detached from its associated coated fiber after having reached its equilibrium swelling state.
  • a first embodiment is a water-swellable, radiation curable coating composition for a fiber including an acrylic acid, a salt of an acrylic acid, a monofunctional ethylenically unsaturated network former, a photoinitiator, a viscosity modifier, an amount of water, and a multifunctional crosslinker, wherein the water-swellable, radiation curable coating composition is a liquid at room temperature.
  • Such compositions are suitable for elongated thin fibers, such as those made from plastic or glass.
  • such compositions are suitable for coating fibers comprised of ultra-high molecular weight polyethylene polymers, such as Dyneema ® .
  • Dyneema ® ultra-high molecular weight polyethylene polymers
  • compositions described herein are particularly suitable for use in coating optical fibers.
  • compositions according to the present invention which in addition to being water-swellable, are uniquely tailored to be optimally performing in the optical fiber application and to meet the requirements of the optical fiber coating process.
  • processing requirements for the composition include UV curability, being liquid at room
  • compositions according to the present invention may be considered superabsorbent polymers (SAP).
  • SAPs are swellable thermoset networks that absorb and retain extremely large quantities of a liquid relative to their own mass.
  • UV-curable SAP compositions are known, and are described in, i.a., EP1522545.
  • SAPs are generally based on crosslinked polymeric chains formed from, (meth)acrylamide or (meth)acrylic acid monomers.
  • the polymer chains formed contain a large number of carboxyl groups. Hydrogen atoms are released through contact with water, resulting in the formation of carboxylate groups. It is believed, without wishing to be bound by any theory, that these carboxylate groups are mutually repellent and create a scaffolding in the polymer network whereby passing water molecules may be encased and trapped.
  • compositions according to certain embodiments of the present invention are liquid at room temperature. This preserves the possibility that such compositions are processable in optical fiber coating applications, and further ensures that the SAP constituents within the formulation are generally dispersed homogeneously or dissolved throughout the liquid resin.
  • a liquid SAP material is advantageous in optical fiber applications over powderized or particle-based SAP systems, because liquid systems obviate the health and safety concerns associated with working with powders, and they further mitigate the occurrence of SAP particle-induced microbends which would produce an undesirable signal loss (aka microbend- induced attenuation) in the corresponding optical fiber.
  • many common SAP powders possess a particle size that is as large or larger than the optimal coating thickness, it is preferable to use liquid-based systems where particle size is not a constraint the system design.
  • the liquid composition includes an acrylic acid, an acrylic acid salt, a monofunctional ethylenically unsaturated network former, a photoinitiator, a viscosity modifier, an amount of water, a multifunctional crosslinker, and further optionally one or more additives.
  • an acrylic acid an acrylic acid salt
  • a monofunctional ethylenically unsaturated network former a monofunctional ethylenically unsaturated network former
  • a photoinitiator a viscosity modifier
  • an amount of water a multifunctional crosslinker
  • additives an additives.
  • the composition includes an acrylic acid.
  • the presence of the acrylic acid in the final composition is optional. However, Inventors have discovered that the presence of a residual amount of un-neutralized acrylic acid in the final formulation may contribute to ensuring the homogeneity of the composition, in that it helps to minimize the precipitation of the acrylic acid salt after formulation.
  • the acrylic acid is present in an amount, relative to the weight of the entire water-swellable, radiation curable coating composition for an optical fiber, from 0 wt.% to 60 wt.%, or from 10 wt.% to 60 wt.%, or 15 wt.% to 40 wt.%, or 18 wt. % to 35 wt.%, or 20 wt.% to 30 wt.%.
  • the relative quantity of the acrylic acid in the formulation may alternatively be described in terms of molality.
  • the concept of molality which is a representation of the number of moles of a particular substance per given unit mass, is well known.
  • the SI unit for molality is moles per kilogram. It may be determined by dividing the mass of the particular component to be measured per 1 kilogram of the entire composition by the molar mass of that component. The molar mass, meanwhile, is determined by multiplying the standard atomic weight (of the idealized compound to be measured) by the constant 1 x 10 "3 kg/mol.
  • the acrylic acid is present, in an amount relative to the entire water-swellable, radiation curable coating composition for an optical fiber expressed in terms of molality, from 0 to 4.2 mol/kg, or from 0.14 to 4.2 mol/kg, or from 0.7 to 2.1 mol/kg.
  • the relative quantity of the acrylic acid in the formulation may alternatively be described in terms of acryloyl equivalents.
  • the method for determining equivalents (such as acryloyl equivalents) is similar to molality and is also well-known, expressed in, i.a., US 7,183,040.
  • the number of acryloyl equivalents of a particular component in the composition is calculated in accordance with the formula:
  • Wt% is the weight in kilograms of the component to be measured relative to that of 1 kg of the entire composition
  • N is the number of acryloyl groups in an idealized molecule of component Z
  • Mwt is the molecular weight of an idealized molecule of the particular compound to be measured.
  • Wt% is the weight in kilograms of the component to be measured relative to that of 1 kg of the entire composition
  • N is the number of acryloyl groups in an idealized molecule of component Z
  • Mwt is the molecular weight of an idealized molecule of the particular compound to be measured.
  • the acryloyl equivalents will not differ from the molality expressed above.
  • the total composition possesses from about 0.14 to about 4.2 acryloyl equivalents, or from 0.7 to 2.1 acryloyl equivalents by virtue of the inclusion of the acrylic acid component.
  • the acrylic acid component contributes from 0.14 to about 4.2, or from 0.7 to 2.1 acryloyl equivalents into the total composition.
  • composition for an optical fiber does not possess a detectable amount of acrylic acid itself, an acrylic acid would have been used as a reactant to form a salt derivative of an acrylic acid, which will be present.
  • the acrylic acid may be present in varying degrees of neutralization.
  • the degree of neutralization refers to the relative quantity by weight, expressed as a percent, of the starting acrylic acid that is converted to an acrylic acid salt (i.e. neutralized) by a suitable base. It may be determined in the final formulation by dividing the total amount, by weight, of the acrylic acid salt by the total amount, by weight, of the acrylic acid salt plus the (un-neutralized) acrylic acid.
  • composition of the present invention also includes an acrylic acid salt, which is the reaction product of the acrylic acid and a base.
  • the base selected can be any suitable alkaline component, including basic salts.
  • a basic salt itself is the reaction product of the neutralization of a strong base with a weak acid, which indicates that basic salts themselves are also bases.
  • a basic salt includes salts containing an ionizable hydroxyl group.
  • An example of a basic salt is an alkali salt.
  • An alkali salt is a water-soluble hydroxide of alkali metals and/or alkaline earth metals. Common examples of alkali salts include sodium hydroxide, potassium hydroxide, lye, calcium hydroxide, and magnesium hydroxide, although others exist as will be understood by the person having ordinary skill in the art.
  • the alkali salt comprises a lithium, sodium, or potassium cation.
  • the acrylic acid salt is the reaction product of an acrylic acid and an ionic compound consisting of an alkali metal cation and a hydroxide anion.
  • the alkali metal may be selected from any of the appropriate group I elements, including lithium, sodium, potassium, rubidium, cesium, or francium.
  • the ionic compound possesses a sodium cation, which, upon reaction with acrylic acid, results in the formation of a salt in the form of sodium acrylate.
  • the acrylic acid salt is useful in enabling the successful formulation of a water-swellable radiation curable coating composition for an optical fiber in several respects. First, it contributes to the improved water swellability of the coating into which it is incorporated. It also enables the formulation of a cured coating with greater integrity, as indicated by its tendency to effectuate an increase in the equilibrium modulus value of its associated coating.
  • the degree of neutralization of the acrylic acid is linked to an improvement in the speed at which the coating composition into which it is incorporated is processable in optical fiber coating applications.
  • the coating composition's ability to cure quickly during optical fiber drawing or inking processing is improved as the percentage of the initial acrylic acid which is converted to a salt increases. This is beneficial in optical fiber coating applications, wherein it is highly desirable to effectuate curing at high speeds and/or with reduced energy input. It is believed, without wishing to be bound by any theory, that the degree of neutralization is tied to a reduction of oxygen-inhibition, a phenomenon which is known to have a chilling effect on free-radical polymerization kinetics.
  • the degree of neutralization does not appear to have a significant effect on initial swelling performance, Inventors believe that if the degree of neutralization becomes too low, the optical fiber coatings formed therefrom tend to exhibit a degradation of swelling performance over time. Without wishing to be bound by any theory, this may be the result of a large amount of un-neutralized acrylic acid's contribution to the secondary formation of additional network crosslinks over time.
  • the reaction of the acrylic acid and the basic salt neutralizes at least 10% of the acrylic acid, more preferably at least 25% of the acrylic acid, or at least 33% of the acrylic acid, or at least 50% of the acrylic acid, or at least 75% of the acrylic acid, or at least 90% of the acrylic acid.
  • an alkali salt neutralizes between 10-100%) of the acrylic acid by weight, relative to the amount of acrylic acid present before the reaction, or between 25-90%) by weight, or between 33-95%) by weight, or between 50-98%) by weight, or between 75- 100%) by weight.
  • the acrylic acid possesses a degree of neutralization of between 10-100%, or between 25-99%, or between 33-98%, or between 50-95%, or between 75- 90%).
  • the degree of neutralization is at least 10%, or at least 20%, or at least 30%), or at least 40%, or at least 50%, or at least 60%, or at least 70%, or at least 80%, or at least 90%), or at least 95%, or at least 98%.
  • the degree of neutralization is approximately 100%.
  • the ratio of the un-neutralized acrylic acid to the amount of acrylic acid which has been neutralized by the basic salt that is present in the liquid swellable radiation curable coating for an optical fiber may also play an important role in determining that composition's cure speed during the coating and curing process, as well as its potential swell behavior once cured on an optical fiber.
  • the water-swellable radiation curable coating composition for an optical fiber comprises a ratio of the acrylic acid to the acrylic acid salt from about 12: 1 to about 1 : 12, or from about 6: 1 to about 1 :6, or from about 3 : 1 to about 1 : 1.
  • the aforementioned ratios may be either expressed as molar ratios or in terms of ratios by weight.
  • the water-swellable radiation curable coating composition for an optical fiber may comprise any suitable amount of an acrylic acid salt, such as, relative to the weight of the entire water-swellable, radiation curable coating composition for an optical fiber an amount of about 1 wt.% to about 30 wt.%, or from about 5 wt.% to about 15 wt.%.
  • the total amount of the acrylic acid-derived components is present in an amount, relative to the entire composition, from about 1.4 to about 8.3 mol/kg, or from 2.1 to 5.6 mol/kg, or from 2.5 to 4.9 mol/kg, or from, 2.8 to 4.2 mol/kg.
  • the water-swellable radiation curable coating composition for an optical fiber may include at least one compound that is ethylenically unsaturated and contributes to ensuring the homogeneous dispersion of the SAP components.
  • the ethylenically unsaturated component comprises an acrylate ester or an acrylamide.
  • the acrylate esters or acrylamides may be of any suitable molecular weight but are preferably monomeric.
  • the ethylenically unsaturated component is monofunctional.
  • “monofunctional” means the pertinent component possesses an average of from 0.9 to 1.1 functional groups per molecule.
  • the functional groups are acryloyl groups.
  • acrylic acid esters are methyl-, ethyl-, n-butyl- and 2- ethylhexyl (2EHA)- esters.
  • Some specific examples include 2-ethylhexyl acrylate, diethylene glycol diacrylate, methyl acrylate, ethyl acrylate, polyacrylic acid, n-butyl acrylate, hydroxypropyl acrylate, and dimethyl aminoethyl acrylate.
  • lower molecular weight monomers containing one double bond are alkyl or hydroxyalkyl acrylates, for example 2-hydroxyethyl acrylate, isobornyl acrylate, and methyl and ethyl acrylate.
  • these monomers are acrylonitrile, acrylamide, N-substituted acrylamides such as n-(2-hydroxypropryl)acrylamide, N-isopropylacrylamide, vinyl esters such as vinyl acetate, styrene, alkylstyrenes, halostyrenes, N-vinylpyrrolidone (such as although other ethylenically unsaturated monomers such as n-vinyl pyrrolidone (such as 1 -vinyl -2- pyrrolidone), N-vinyl caprolactam, vinyl chloride and vinylidene chloride.
  • acrylonitrile acrylamide
  • N-substituted acrylamides such as n-(2-hydroxypropryl)acrylamide, N-isopropylacrylamide
  • vinyl esters such as vinyl acetate, styrene, alkylstyrenes, halostyrenes
  • the water-swellable radiation curable coating composition for an optical fiber includes an ethylenically unsaturated swelling compound that is a hydroxy functional acrylate compound.
  • hydroxy functional acrylate compounds include 2-hydroxypropyl acrylate, 3 -hydroxy propyl acrylate, hydroxy ethyl acrylate, 4 hydroxy butyl acrylate, 2,3-dihydroxy propyl acrylate, 2-hydroxy-l-(hydroxymethyl)ethyl acrylate, or 2-acrylamido-2-m ethyl- 1- propanesulfonic acid.
  • the ethylenically unsaturated compound is an ethoxylated acrylate ether.
  • ethoxylated acrylate ethers include methoxy (poly ethylene glycol) acrylate, ethoxy (polyethylene glycol) acrylate, 2-(2-ethoxyethoxy)ethyl acrylate, ethylene glycol methyl ether acrylate, diethylene glycol methyl ether acrylate, triethylene glycol methyl ether acrylate, tetratethylene glycol methyl ether acrylate, ethylene glycol ethyl ether acrylate, diethylene glycol ethyl ether acrylate, triethylene glycol ethyl ether acrylate, tetratethylene glycol ethyl ether acrylate, diethylene glycol -2-ethylhexylether acrylate.
  • the water- swellable radiation curable coating composition for an optical fiber may contain the ethylenically unsaturated network former in an amount by weight, relative to the weight of the entire water- swellable, radiation curable coating composition for an optical fiber of about 5 wt.% to about 50 wt.%, more preferably from about 10 wt.% to about 30 wt.%.
  • the monofunctional ethylenically unsaturated network former may be present in an amount, relative to the entire composition, from about 0.38 to about 3.8 mol/kg, or from about 0.75 to about 2.3 mol/kg.
  • the entire composition will possess from 0.38 to about 3.8 acryloyl equivalents by virtue of the monofunctional ethylenically unsaturated network former, or from about 0.75 to about 2.3 acryloyl equivalents by virtue of the monofunctional ethylenically unsaturated network former.
  • the total amount of monofunctional ethylenically unsaturated network formers present in the composition will contribute from about 0.38 to about 3.8, or from about 0.75 to 2.3 acryloyl equivalents.
  • compositions of the present invention include a photoinitiator.
  • the composition includes at least one free-radical photoinitiator.
  • the photoinitiator is a compound that chemically changes due to the action of light or the synergy between the action of light and the electronic excitation of a sensitizing dye to produce at least one of a radical, an acid, and a base.
  • the free-radical photoinitiator is an acylphosphine oxide photoinitiator.
  • Acylphosphine oxide photoinitiators are disclosed for example in U.S. Pat. Nos. 4324744, 4737593, 5942290, 5534559, 6020529, 6486228, and 6486226.
  • acylphosphine oxide photoinitiators are bisacylphosphine oxides (BAPO) or monoacylphosphine oxides (MAPO).
  • the bisacylphosphine oxide photoinitiators are of the formula I:
  • R50 is C1-C12 alkyl, cyclohexyl or phenyl which is unsubstituted or is substituted by 1 to 4 halogen or Ci-C 8 alkyl;
  • R51 and R52 are each independently of the other Ci-C 8 alkyl or Ci-C 8 alkoxy;
  • R53 is hydrogen or Ci-C 8 alkyl
  • R54 is hydrogen or methyl.
  • R50 is C2-C10 alkyl, cyclohexyl or phenyl which is unsubstituted or is substituted by 1 to 4 C1-C4 alkyl, CI or Br.
  • R50 is C 3 -C 8 alkyl, cyclohexyl or phenyl which is unsubstituted or is substituted in the 2-, 3-, 4- or 2,5-positions by Ci- C 4 alkyl.
  • R50 is C4-C12 alkyl or cyclohexyl
  • R51 and R52 are each independently of the other Ci-C 8 alkyl or Ci-C 8 alkoxy
  • R 53 is hydrogen or Ci-C 8 alkyl.
  • R51 and R52 are C1-C4 alkyl or Ci-C4alkoxy and R 53 is hydrogen or C1-C4 alkyl.
  • R51 and R 5 2 are methyl or methoxy and R 53 is hydrogen or methyl.
  • R51, R52 and R 53 are methyl.
  • R51, R52 and R 53 are methyl and R54 is hydrogen.
  • R50 is C 3 -C 8 alkyl.
  • R51 and R52 are methoxy
  • R 53 and R54 are hydrogen and R50 is is isooctyl.
  • R50 is isobutyl.
  • R50 is phenyl.
  • the present bisacylphosphine oxide photoinitiator is for example bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide (CAS# 162881-26-7) or is bis(2,4,6-trimethylbenzoyl)-(2,4-bis-pentyloxyphenyl)phosphine oxide.
  • the monoacylphosphine oxide photoinitiators are of the formula II:
  • Ri and R 2 independently of one another are Ci-Cnalkyl, benzyl, phenyl which is unsubstituted or substituted from one to four times by halogen, Ci-C 8 alkyl and/or Ci- C 8 alkoxy, or are cyclohexyl or a group -COR3, or
  • R 3 is phenyl which is unsubstituted or substituted from one to four times by Ci-C 8 alkyl, Ci- C 8 alkoxy, Ci-C 8 alkylthio and/or halogen;
  • R 4 is Ci-C 8 alkyl, phenyl or benzyl.
  • Ri is -OR4.
  • R 2 is phenyl which is unsubstituted or substituted from one to four times by halogen, Ci-C 8 alkyl and/or Ci-C 8 alkoxy.
  • R 3 is phenyl which is unsubstituted or substituted from one to four times by Ci-C 8 alkyl.
  • the present monoacylphosphine oxide is 2,4,6- trimethylbenzoylethoxyphenylphosphine oxide (CAS# 84434-11-7) or 2,4,6- trimethylbenzoyldiphenylphosphine oxide (CAS# 127090-72-6).
  • compositions according to the present invention may also employ further
  • photoinitiators for example a-h droxy ketone photoinitiators of the formula III:
  • R11 and R12 independently of one another are hydrogen, Ci-C 6 alkyl, phenyl, Ci-C 6 alkoxy, OSiRi 6 (Riv) 2 or -0(CH 2 CH 2 0) q -Ci-C 6 alkyl, or
  • R11 and R12 together with the carbon atom to which they are attached, form a cyclohexyl ring
  • Ri3 is OH, C1-C16 alkoxy or -0(CH 2 CH 2 0) q -Ci-C 6 alkyl;
  • n is a number from 2 to 10;
  • Ri6 and Ri7 independently of one another are Ci-C 8 alkyl or phenyl;
  • G 3 and G 4 independently of one another are end groups of the polymeric structure, preferably hydrogen or methyl.
  • a-hydroxy ketone photoinitiators that are of interest are those in which Rn and
  • a-hydroxy ketone photoinitiators are those in which Rn and
  • Ri2 independently of one another are methyl or ethyl or Rn and R12, together with the carbon atom to which they are attached, form a cyclohexyl ring, R13 is hydrogen and R14 is hydrogen, Ci- C 4 alkyl, C1-C4 alkoxy or -OCH2CH2OH.
  • R14 is
  • the present a-hydroxy ketone photoinitiator is for example a-hydroxy cyclohexylphenyl ketone or 2-hydroxy-2-methyl-l -phenyl- 1-propanone.
  • Straight or branched chain alkyl is for example, methyl, ethyl, propyl, isopropyl, butyl, isobutyl, sec-butyl, tert-butyl, pentyl, isopentyl, isooctyl, hexyl, heptyl, octyl, nonyl, decyl or dodecyl.
  • alkoxy or alkylthio are of the same straight or branched chains.
  • Photoinitiators according to the present invention may be employed singularly or in combination of one or more as a blend.
  • Suitable photoinitiator blends are for example disclosed in U.S. Pat. No. 6,020,528 and U.S. Pat. app. No. 60/498,848.
  • the present PI is for example disclosed in U.S. Pat. No. 6,020,528 and U.S. Pat. app. No. 60/498,848.
  • the present PI blends are for example disclosed in U.S. Pat. No. 6,020,528 and U.S. Pat. app. No. 60/498,848.
  • the present PI is for example disclosed in U.S. Pat. No. 6,020,528 and U.S. Pat. app. No. 60/498,848.
  • the present PI is for example disclosed in U.S. Pat. No. 6,020,528 and U.S. Pat. app. No. 60/498,848.
  • photoinitiator blends are for example a mixture of bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide (CAS# 162881-26-7) and 2,4,6,-trimethylbenzoylethoxyphenylphosphine oxide (CAS# 84434-11-7) in ratios by weight of about 1 : 11, 1 : 10, 1 :9, 1 :8 or 1 :7.
  • Another especially suitable PI blend is a mixture of bis(2,4,6- trimethylbenzoyl)phenylphosphine oxide, 2,4,6,-trimethylbenzoylethoxyphenylphosphine oxide and 2-hydroxy-2-m ethyl- 1 -phenyl- 1-propanone (CAS# 7473-98-5) in weight ratios of for instance about 3 : 1 : 15 or 3 : 1 : 16 or 4: 1 : 15 or 4: 1 : 16.
  • Another suitable PI blend is a mixture of bis(2,4,6- trimethylbenzoyl)phenylphosphine oxide and 2-hydroxy-2-methyl-l-phenyl-l-propanone in weight ratios of for instance about 1 :3, 1 :4 or 1 :5.
  • the present acylphosphine oxide PI or PI blend is present in the radiation-curable compositions from about 0.2 to about 10% by weight, based on the weight of the composition.
  • the PI or PI blend is present from about 0.5 to about 8%, about 1 to about 7%, or about 2, 3, 4, 5 or 6% by weight based on the weight of the radiation- curable composition.
  • Suitable photoinitiators according to this invention are for or example, other mono- or bisacylphosphinoxides such as diphenyl-2,4,6-trimethylbenzoylphosphine oxide or bis(2,6- dimethoxybenzoyl)-2,4,4-trimethylpentylphosphineoxide; a-hydroxy ketones, such as 1- hydroxycyclohexylphenylketone or 2-hydroxy- 1 -[4-(2-hydroxyethoxy)phenyl]-2-methyl- 1 - propanone; a-aminoketones, such as 2-methyl-l-[4-(methylthio)phenyl]-2-(4-mo holinyl)-l- propanone, 2-benzyl-2-(dimethylamino)-l-[4-(4-morpholinyl)phenyl]-l-butanone, 2-(4- methylbenzyl-2-(dimethylamino)-l-[4
  • Suitable photoinitiators employed according to this invention are for example oxime esters as disclosed in U.S. Pat. No. 6,596,445.
  • a suitable oxime ester photoinitiator is for example: [081]
  • certain so-called cationic photoinitiators such as those of the sulfonium or iodonium salt type, also generate free radicals and could be used as photoinitiators in embodiments of the present invention.
  • Such photoinitiators are described in, i.a., U.S. Pat. No. 9,708,442.
  • Suitable photoinitiators according to this invention are for example phenyl glyoxalates, for example as disclosed in U.S. Pat. No. 6,048,660.
  • Y is Ci-Coalkylene, cyclohexylene, C2-C4oalkylene interrupted one or more times by cyclohexylene, O, S, or NR30, and R30 is hydrogen, Ci-Coalkyl or phenyl, preferably Y is CH2CH2-
  • photoinitiators can be employed in compositions according to the present invention in any suitable amount, and may be chosen singly or in combination of one or more of the types enumerated herein.
  • the photoinitiator component is present in an amount, relative to the entire weight of the liquid, water- swellable composition for coating an optical fiber, from about 0.1 wt.% to about 10 wt.%, or from about 0.1 wt.% to about 5 wt.%, or from about 1 wt.% to about 5 wt.%.
  • composition into which they are incorporated although it is desirable that they do not significantly hinder this important coating property.
  • the viscosity modifiers described herein typically would be included to increase the viscosity of the composition into which they are incorporated, because the aforementioned SAP-related constituents often yield compositions with a viscosity that is too low to be suitable in optical fiber processing applications.
  • viscosity modifiers that reduce the overall viscosity of the composition into which they are associated. If the viscosity of the composition is too high, the coating may not sufficiently flow through the coating die to enable optimum coverage onto the previously coated layer, either.
  • the viscosity modifier is water soluble.
  • the water- soluble viscosity modifier comprises a polyvinyl alcohol, a polyvinyl pyrrolidone, a starch, a modified cellulose, a gelatin, a polyglycol compound such as polyethylene glycol with a molecular weight from 250,000 to 4,000,000 g/mol, or a polyacrylic acid.
  • Polyvinyl alcohols are water-soluble synthetic polymers which possess the idealized formula [CH2CH(OH)] n . They may be known analogously and/or commercially as PVOH;
  • Polyvinyl pyrrolidone is a water-soluble polymer made from the monomer N- vinylpyrrolidone. It may be known analogously and/or commercially as PVP, Povidone,
  • Copovidone PVPP, Crospovidone, Polyvidone, PNVP, Poly[l-(2-oxo-l-pyrrolidinyl)ethylen], 1- Ethenyl-2-pyrrolidon homopolymer, or l-vinyl-2-pyrrolidinon-polymere.
  • a starch is a polymeric carbohydrate consisting of a large number of glucose units joined by glycosidic bonds. It may possess any suitable molecular mass, and is represented by the chemical formula (CeHioOs).
  • modified cellulosic compounds include those which comprise a methyl cellulose or hydroxyethyl cellulose compound.
  • Certain compounds are particularly preferred for use as a viscosity modifier because their inclusion improves the processability of the composition into which they are incorporated without significantly adversely affecting the composition's swellability.
  • polyvinyl pyrrolidone for example, is a preferred viscosity modifier because, when used in effective quantities at a suitable molecular weight, it sufficiently increases the viscosity of the composition into which it is incorporated to a level that is satisfactory for ensuring processing in optical fiber coating applications, all without inducing a significant detrimental effect on the ability of that composition to swell after introduction to water.
  • the liquid water-swellable radiation curable coating composition for an optical fiber includes a polyvinyl pyrrolidone compound.
  • the polyvinyl pyrrolidone may possess any suitable molecular weight, for example from 1 kilodalton (kDa) to 5 megadalton (MDa), or from 5 kDa to 1000 kDa, or from 50 kDa to 500 kDa, or from 75 kDa to 300 kDa, of from 100 kDa to 200 kDa.
  • the polyvinyl pyrrolidone in order to sufficiently increase the viscosity of the composition into which it is incorporated, possesses a high molecular weight, such as from 100 kDa to 300 kDa, or from 120 kDa to 200 kDa.
  • a viscosity modifier of a sufficiently high molecular weight should be utilized in suitable amounts, as will be appreciated by those of ordinary skill in the art to which this invention applies.
  • the viscosity modifier may be present in any suitable amount by weight, relative to the weight of the entire water-swellable, radiation curable coating composition for an optical fiber, such as from about 5 wt.% to about 40 wt.%, or from about 8 wt.% to about 30 wt.%, or from about 10 wt.% to about 25 wt.%, or from about 15 wt.% to about 20 wt.%.
  • the viscosity modifier should be included in any sufficient amount to ensure the composition into which it is incorporated possesses a viscosity suitable for processing on coating an optical fiber, such as the viscosities at which compositions are typically coated and cured onto an optical fiber on a draw tower or inking machine.
  • the viscosity modifier is included in an amount according to well- known methods to bring the viscosity of the water-swellable, radiation curable coating composition into which it is incorporated to a level at 25° C from about 500 centipoise (cPs) to about 5000 cPs, or from about 600 cPs to about 4000 cPs, or from about 700 cPs to about 3000 cPs, or from about 800 cPs to about 2000 cPs, or from 800 cPs to 1200 cPs.
  • cPs centipoise
  • the viscosity modifier is included in an amount according to well-known methods to bring the viscosity of the water-swellable, radiation curable coating composition into which it is incorporated to a level at 25° C from around 1200 to about 3000 cPs, or from about 1400 to about 2800 cPs, or from about 1600 to about 2700 cPs, or from about 1700 to about 2500 cPs.
  • the exact viscosity of the formulation to be processed will be tuned according to values known in the art depending upon several factors, including the thickness of the water-swellable, radiation curable coating composition intended to be applied, along with the line or inking speed at which the coating application process occurs.
  • compositions according to the present invention often involve the inclusion of water. That is, to ensure homogeneity or to avoid safety, environmental, or handling concerns, many of the components elsewhere described are provided commercially as liquids, which may take the form of aqueous solutions. As such, water will often be present (even if unintentionally) in the compositions according to the present invention. However, Inventors have determined that the swelling performance of the coating actually improves if water is added to the water-swellable radiation curable composition for coating an optical fiber before it becomes cured and subsequently exposed to external fluids.
  • the water-swellable radiation curable coating composition for an optical fiber also includes an amount of water.
  • the water may be present, in an amount by weight, relative to the weight of the entire water-swellable, radiation curable coating composition for an optical fiber of about 0.1 wt.% to about 50 wt.%, or from about 5 wt.% to about 45 wt.%, or from about 10 wt.% to about 40 wt.%, or from about 15 wt.% to about 35 wt.%.
  • the coating integrity i.e. modulus
  • cure speed will be adversely affected such that a viable coating for optical fiber applications cannot be formed.
  • compositions according to the present invention should also include at least one crosslinker. That is, they include at least one reagent that is incorporated in the thermoset material in order to form additional network crosslinks, which are small region in a macromolecule from which at least four chains emanate, and which is formed by reactions involving sites or groups on existing macromolecules or by interactions between existing macromolecules.
  • additional cross-linking is required to ensure the coating will retain significant structural integrity upon exposure to water.
  • the coating does not maintain sufficient integrity after it has swelled, the coating will easily break apart into many small pieces during the swelling process. If it does so, the coating will enable channels or pathways for untrapped water to flow through, in turn limiting the overall longitudinal water blocking effectiveness in an optical fiber application.
  • the water-swellable radiation curable coating composition for an optical fiber of the present invention comprises a crosslinker that induces additional network crosslinks to the crosslinked polymer chains formed by the ethylenically unsaturated network former component described elsewhere herein.
  • crosslinker comprises a free- radically polymerizable compound with an average of greater than 1.0 functional groups, wherein the functional groups are preferably acrylate or acrylamide functional groups.
  • the crosslinker is multifunctional. As used herein, "multifunctional" means the pertinent component possesses an average of at least 1.9 functional groups per molecule.
  • the multifunctional crosslinker comprises a difunctional compound, that is, a compound with an average number of functional groups of from 1.9 to 2.1, or preferably an average of 2.0 functional groups.
  • the ethylenically unsaturated component comprises a polyfunctional compound, that is, a compound with an average number of functional groups of at least 2.1.
  • the crosslinker preferably comprises a multifunctional acrylate or a multifunctional acrylamide.
  • the multifunctional crosslinker is difunctional, or possesses an average of from 1.9 to 2.5 functional groups per molecule.
  • the multifunctional crosslinker is trifunctional, or possesses an average of from greater than 2.5 to 3.5 functional groups per molecule.
  • the multifunctional crosslinker is tetrafunctional, or possesses an average of from greater than 3.5 to 4.5 functional groups per molecule.
  • the multifunctional crosslinker is
  • the multifunctional crosslinker is hexafunctional, or possesses an average of from greater than 5.5 to 6.5 functional groups per molecule.
  • multiple multifunctional crosslinkers of the above types may be used singly or in any combination.
  • the crosslinkers should be selected so that at least one possesses at least one functional group which is the same as at least the functional group of the monofunctional ethyl enically unsaturated network- forming component used, as described elsewhere herein.
  • the water-swellable radiation curable coating composition for an optical fiber may include an acrylate-functional crosslinker.
  • crosslinkers include ethylene glycol diacrylate, diethylene glycol diacrylate, triethylene glycol diacrylate, tetra ethylene glycol diacrylate, ethoxylated hexane diol diacrylate, trimethylolpropane ethoxylate, trimethylolpropane diacrylate, trimethylolpropane triacrylate, methyl ether diacrylate, neopentyl glycol diacrylate, 1,3-butanediol diacrylate, glycerol-l,3-diglycerolate diacrylate, 1,6- hexanediyl bis[oxy-2-hydroxy-3, l-propanediyl] bis acrylate, pentaerythritol triacrylate, or ethoxylated pentaerythritol triacrylate,
  • the water-swellable radiation curable coating composition for an optical fiber includes an acrylamide-functional crosslinker.
  • crosslinkers include ⁇ , ⁇ -methylene bisacrylamide or an n-n-ethylene bisacrylamide.
  • Examples of additional multifunctional crosslinkers containing more than one double bond are polyethylene glycol diacrylates, ethylene glycol diacrylate, propylene glycol diacrylate, neopentyl glycol diacrylate, hexamethylene glycol diacrylate, bisphenol A diacrylate, 4,4'-bis(2- acryloyloxyethoxy)diphenylpropane, trimethylolpropane triacrylate, pentaerythritol triacrylate and tetraacrylate, vinyl acrylate, divinyl benzene, divinyl succinate, diallyl phthalate, triallyl phosphate, triallyl isocyanurate, divinyl adipate, or tris(2-acryloylethyl)isocyanurate.
  • the multifunctional crosslinker containing more than one double bond possesses a number average molecular weight from 200 to 20,000 g/mol, or preferably from 200 to 15,000 g/mol, or even more preferably from 400 to 10000 g/mol.
  • compositions of the present invention may include any suitable amount of crosslinker.
  • crosslinker any suitable amount of crosslinker.
  • the multifunctional crosslinker component may be used in order to ensure the composition into which it is incorporated is simultaneously both optimally longitudinally water-blocking and suitable for use in an optical fiber coating process. If the network crosslink density is too low, the coating will not possess sufficient integrity to maintain a unitary structure during water exposure, in turn limiting the coating's ability to be sufficiently longitudinally water blocking in an optical fiber application. If the crosslink density is too high, however, the coating itself will not be sufficiently water-swellable.
  • the multifunctional crosslinker is present in an amount by weight, relative to the weight of the entire water-swellable, radiation curable coating composition for an optical fiber, of from greater than 0.1 wt.% to less than 5 wt.%, more preferably from about 0.5 wt.% to about 3 wt.%.
  • the multifunctional crosslinker is present in an amount, relative to the entire composition, from about 3.8 to about 190 mmol/ kg, or from about 19 to 110 mmol/kg. Additionally, in an embodiment the entire
  • composition possesses from about 1.9 to about 95 acryloyl milliequivalents by virtue of the multifunctional crosslinker, or from about 9.5 to about 55 acryloyl milliequivalents by virtue of the multifunctional crosslinker. Stated alternatively, the total amount of multifunctional crosslinkers present in the total composition will contribute from about 1.9 to about 95, or from about 9.5 to about 55 acryloyl milliequivalents.
  • compositions of the present invention may optionally further include one or more additives.
  • additives may be added as is required for the particular design criteria and application requirements in which the particular water-swellable coating will be used.
  • the water-swellable radiation curable coating composition for an optical fiber will, by virtue of its location as the outermost coated layer of the coated optical fiber, be useful for fiber identification purposes.
  • the liquid, water-swellable composition for coating an optical fiber further includes an ink.
  • an ink it is preferable that the composition is applied to the secondary coating of the optical fiber in the inking process, as this will ensure that no additional processing is required to impart the water-blocking characteristics to the coated optical fiber.
  • Inks include a colorant such as a photoreducible dye, for example xanthene, benzoxanthene, benzothioxanthene, thiazine, pyronine, porphyrin or acridine dyes, and/or a trihalomethyl compound which can be cleaved by radiation. Similar compositions are described, for example, in U.S. Pat. No. 5,229,253. Inks may also include other conventional colorants such as fluorescent whiteners, pigments, or dyes.
  • a colorant such as a photoreducible dye, for example xanthene, benzoxanthene, benzothioxanthene, thiazine, pyronine, porphyrin or acridine dyes, and/or a trihalomethyl compound which can be cleaved by radiation. Similar compositions are described, for example, in U.S. Pat. No. 5,229,253. Inks may also include other conventional colorants
  • the ink is present in an amount, relative to the weight of the entire water-swellable, radiation curable coating composition for an optical fiber of about 0.01 wt.% to about 5 wt.%), or from about 0.05 wt.%> to about 2 wt.%, or from about 0.1 wt.%> to about 1 wt.%>.
  • Additives are also typically added to optical fiber coatings to achieve certain desirable characteristics such as improved shelf life, improved coating oxidative and hydrolytic stability, improved surface properties, and the like.
  • desirable additives There are many different types of desirable additives, and the invention discussed herein is not intended to be limited by these, nevertheless they are included in the envisioned embodiments since they have desirable effects.
  • fillers examples include fillers, slip additives, wetting agents or levelling assistants.
  • Thermal inhibitors which are intended to prevent premature polymerization, may also be used.
  • examples include hydroquinone, hydroquinone derivatives, p-methoxyphenol, beta-naphthol or sterically hindered phenols, such as 2,6-di(tert-butyl)-p-cresol.
  • the shelf life in the dark can be increased, for example, by using copper compounds, such as copper naphthenate, copper stearate or copper octoate, phosphorus compounds, for example triphenylphosphine, tributylphosphine, triethyl phosphite, triphenyl phosphite or tribenzyl phosphite, quaternary ammonium compounds, such as tetramethylammonium chloride or trimethylbenzylammonium chloride.
  • copper compounds such as copper naphthenate, copper stearate or copper octoate
  • phosphorus compounds for example triphenylphosphine, tributylphosphine, triethyl phosphite, triphenyl phosphite or tribenzyl phosphite
  • quaternary ammonium compounds such as tetramethylammonium chloride or trimethylbenzylammonium chloride.
  • paraffin or similar wax like substances can be added; these migrate to the surface on commencement of the
  • UV absorbers for example well known commercial UV absorbers of the hydroxyphenylbenzotriazole, hydroxyphenyl-benzophenone, oxalamide or hydroxyphenyl-s-triazine type. It is possible to use individual such compounds or mixtures thereof, with or without the use of sterically hindered relatively non-basic amine light stabilizers (HALS). Sterically hindered amines are for example based on 2,2,6,6- tetramethylpiperidine. UV absorbers and sterically hindered amines are for example:
  • 2-Hydroxybenzophenones include, for example, the 4-hydroxy, 4-methoxy, 4-octyloxy, 4-decyloxy, 4-dodecyloxy, 4-benzyloxy, 4,2',4'-trihydroxy and 2'-hydroxy-4,4'-dimethoxy derivatives.
  • Esters of substituted and unsubstituted benzoic acids include, as for example 4-tert- butylphenyl salicylate, phenyl salicylate, octylphenyl salicylate, dibenzoyl resorcinol, bis(4-tert- butylbenzoyl) resorcinol, benzoyl resorcinol, 2,4-di-tert-butylphenyl 3,5-di-tert-butyl-4- hydroxybenzoate, hexadecyl 3,5-di-tert-butyl-4-hydroxybenzoate, octadecyl 3,5-di-tert-butyl-4- hydroxybenzoate, 2-methyl-4,6-di-tert-butylphenyl 3,5-di-tert-butyl-4-hydroxybenzoate.
  • aromatic carbonyl compounds such as benzophenone derivatives, thioxanthone derivatives, anthraquinone derivatives and 3-acylcoumarin derivatives, and also 3-(aroylmethylene)thiazolines, and also eosine, rhodamine and erythrosine dyes.
  • the curing procedure can be assisted, in particular, by compositions which are pigmented (for example with titanium dioxide), and also by adding a component which forms free radicals under thermal conditions, for example an azo compound such as 2,2'-azobis(4-methoxy- 2,4-dimethylvaleronitrile), a triazene, a diazo sulfide, a pentazadiene or a peroxy compound, such as a hydroperoxide or peroxycarbonate, for example t-butyl hydroperoxide, as described in U.S. Pat. No. 4,753,817.
  • a component which forms free radicals under thermal conditions for example an azo compound such as 2,2'-azobis(4-methoxy- 2,4-dimethylvaleronitrile), a triazene, a diazo sulfide, a pentazadiene or a peroxy compound, such as a hydroperoxide or peroxycarbonate, for example t-butyl hydroperoxide,
  • One or more of the aforementioned additives can be employed in compositions according to the present invention in any suitable amount, and may be chosen singly or in combination of one or more of the types enumerated herein.
  • the additive component is present in an amount, relative to the entire weight of the composition, of from about 0.01 wt.% to about 5 wt.%, more preferably from about 0.1 wt.% to about 2 wt.%.
  • the one or more of the aforementioned additives are included in an amount from about 1 wt.% to about 5 wt.%.
  • the suitability of the composition for forming a water-swellable radiation curable coating composition for an optical fiber may be improved if some of the aforementioned components are formulated in specific quantities relative to each other.
  • the water-swellable radiation curable coating composition for an optical fiber possess specified molar ratios of the acrylic acid and the acrylic acid salt components to the monofunctional ethylenically unsaturated monomer component. In an embodiment, that ratio is from about 1 : 1 to about 9: 1, or from about 1.05: 1 to about 6: 1, or from about 3 :2 to about 4: 1.
  • the water-swellable radiation curable coating composition for an optical fiber possess specified molar ratios of the acrylic acid and the acrylic acid salt components to the multifunctional crosslinker component. In an embodiment, this ratio is from about 24: 1 to about 100,000: 1, or from about 32: 1 to about 1000: 1, or from about 50: 1 to about 200: 1.
  • the water-swellable radiation curable coating composition for an optical fiber possess specified molar ratios of the monofunctional ethylenically unsaturated network former component to the multifunctional crosslinker component. In an embodiment, that ratio is from about 4: 1 to about 1000: 1, or from about 9: 1 to about 200: 1, or from about 20: 1 to about 100: 1.
  • compositions contain compounds possessing acyl groups derived from an acrylic acid. In a preferred embodiment, they further do not contain compounds with acyl groups derived from methacrylic acid.
  • methacrylates, methacrylate esters, and/or methacrylamides are commonly used to produce superior water swellable compositions
  • Inventors have determined that substantial use of methacrylates, methacrylate esters, and/or methacrylamides are not suitable for use in compositions of the present invention. This is because the substantial inclusion of methacrylate-functional components is thought to hinder the cure speed of the composition into which such components are included, such that the composition would no longer remain suitable for the high-speed cure requirements of modern optical fiber coating processes.
  • the composition is substantially free from a methacrylate component.
  • the composition is substantially free from a compound which possesses acyl groups derived from methacrylic acid.
  • the composition possesses less than 3%, or less than 2%, or less than 1%, or less than 0.5% by weight of a compound possessing acyl groups derived from methacrylic acid.
  • the composition comprises one or more compounds possessing free-radically polymerizable functional groups.
  • Such compounds possessing free-radically polymerizable functional groups may be from one of the existing compositional elements; e.g. the monofunctional ethylenically unsaturated network former or the multifunctional crosslinker.
  • the free- radically polymerizable groups in all such compounds consist essentially of acrylate functional groups.
  • a second embodiment is an optical fiber coated with a primary coating, a secondary coating adhered to and surrounding the primary coating, and a water-swellable exterior coating adhered to and surrounding the secondary coating, wherein the water-swellable exterior coating is configured to buckle and detach from the secondary coating at least one point along a section of the coated optical fiber within 3 minutes, or within 2 minutes, or within 1 minute, or within 30 seconds, or within 20 seconds, or within 10 seconds, or within 5 seconds after the coated optical fiber has been submerged in deionized water.
  • FIG. 1 A coated optical fiber according to an aspect of the second embodiment is shown in Figure 1.
  • Fig. 1 a cross-section of a coated optical fiber with a water-swellable exterior coating 10 according to an embodiment of the invention is depicted.
  • Such coated optical fiber with the water-swell able exterior coating 10 includes a glass core 11 having diameter Di, which is surrounded by a cladding 12 having diameter D 2 .
  • the cladding 12 is coated with primary coating 13, which itself is coated with secondary coating 14.
  • a water-swellable coating layer 15 surrounds and contacts the secondary coating, thereby forming the exterior layer of the coated optical fiber.
  • the diameter of optical fibers onto which the water-swellable coating layer 15 is applied is typically around 240 microns, although any size coated optical fiber may be used in accordance with the principles of the current invention, such as 180 - 240 ⁇ , or from 240-250 ⁇ , for example.
  • Detachability of a coating is desirable because it enables the maximization of a particular coating's swelling potential.
  • two coatings of similar film swell capability will not perform identically in terms of longitudinal water-blocking, all else being equal, if one of the coatings is detachable from the coated fiber while the second is not.
  • the first (detachable) coating on fiber will exhibit a higher volumetric swell ratio - and a superior longitudinal water-blocking performance - than the second.
  • Inventors surmise this is because the detachability of a coating is required because it enables the coating to swell unhindered in all directions.
  • the detachment problem is particularly acute in the optical fiber coating context because of the geometry of the successive coatings themselves. That is, localized forces induced by the exterior coating's swelling process may not overcome the significant adhesion to the adjacent layer due in part to the significant contact patch that is inherently formed between two successive coatings in a thin, elongated cylindrical fiber. Regardless, the swelling process builds up axial compressive stress in the coating. If the compressive force exceeds the coating's critical buckling force, the swellable layer will buckle (i.e. form periodical patterns along the axial direction initially with the peak of the buckle shifted in a direction away from the adjacent coating layer) and eventually detach from the fiber, thereby inducing further swelling.
  • a first factor to configure for detachability is via the chemistry of the coating itself. Preferred embodiments of coating with superior swellability and structural integrity are described elsewhere herein, supra. The coatings described herein facilitate the maximum amount of axial stress because they exhibit superior swellability in coated optical fiber applications.
  • a second factor to configure for detachability is via the thickness of the water-swellable coated layer itself. This may be tuned according to known processing methods. Inventors have surprisingly discovered that coatings with thicknesses within certain prescribed ranges facilitate maximum detachability. In an embodiment, therefore, the water-swellable exterior coating possesses a thickness from 0.1 to less than 20 microns, or from 1 to 20 microns, or from 0.2 to 10 microns, or from 0.3 to 5 microns, or from 2 to 5 microns, or from 1 to 4 microns. If the thickness becomes too small, sufficient swelling may not occur. If it becomes too large, consistent detachability may not be ensured quickly enough, and the amount of fibers permissible in a small size buffer tube configuration may be reduced via each coating's relatively enlarged diameter.
  • the coating is processed with a cure dose sufficient to impart a top surface percent reacted acrylate unsaturation %RAU of at least 80%, more preferably at least 90%, or at least 95%, or at least 98%, or at least 99% according to an FTIR method, which is described in, i.a., WO2011/075549 ("The degree of cure of the secondary coating on an optical fiber by FTIR”), which is hereby incorporated by reference in its entirety.
  • the cure intensity may be an important processing parameter which may have an impact on the detachability, swellability, and/or longitudinal water blocking performance of the coating. It has been determined that, ceteris paribus, higher UV intensities will result in shorter kinetic chain lengths and thus lower crosslinking concentrations. This tends to result in an improvement of the swellability and detachability of the coating itself. However, if UV intensities become too high, the ever-shorter kinetic chain lengths result in an impermissibly low crosslink density, which tends to yield a coating which exhibits reduced integrity and becomes more susceptible to disintegration or dissolution during the swelling process.
  • the aforementioned factors should be tuned to ensure that the water-swellable radiation curable coating for an optical fiber according to the present invention is sufficiently swellable regardless of whether it is configured to buckle and/or detach from the coated fiber.
  • This swellability profile is a necessary (but not sufficient) property which the coating must possess to ensure that it facilitates the construction of a system that is sufficiently longitudinally water- blocking. This property may be measured by determining the cured coating's film swelling ratio.
  • the composition possesses a film swelling ratio of greater than about 5 times (x), or greater than about 3 lx, or greater than about 56x, or greater than 80x, or greater than lOOx, or greater than 200x, or greater than 220x.
  • the radiation curable coating possesses, when coated on a 10 mil drawdown film on a glass plate, and cured by 3 passes of 1 J/cm 2 per pass with Fusion 600 W/in D lamps imparting an irradiance of 8 W/cm 2 on a conveyor system, a film swelling ratio of at least 5x, or at least lOx, or at least 20x, or at least 3 Ox, or at least 40x, and less than 300x, or less than 200x, or less than lOOx, or from 5x to 250x, or from 20x to 225x, or from lOx to lOOx, or from 20x to lOOx, or from 40x to 80x, or from 35x to 250x.
  • a third embodiment is a method of applying a liquid, water-swellable coating to a coated optical fiber comprising the steps of providing a coated optical fiber, applying a liquid water- swellable coating composition to an exterior surface of a section of coated optical fiber to form a coated optical fiber with a liquid water-swellable exterior coating composition, and exposing the coated optical fiber with the liquid water-swellable exterior coating composition to a light source capable of emitting ultraviolet radiation to affect curing of said liquid water-swellable exterior coating composition, to form a coated optical fiber with a water-swellable exterior coating, wherein the water-swellable exterior coating is configured to buckle and detach from the coated optical fiber at least one point along the section of the coated optical fiber within 3 minutes, or within 2 minutes, or within 1 minute, or within 30 seconds, or within 20 seconds, or within 10 seconds, or within 5 seconds after the time from which the coated optical fiber with the water-swellable exterior coating has been submerged in deionized water.
  • a particular method of coating optical fibers involves the steps of drawing a glass optical fiber through a draw tower; applying a primary coating composition onto the surface of the glass optical fiber; optionally, exposing the primary coating composition to a first light source capable of emitting ultraviolet radiation to affect curing of said primary coating composition;
  • the water-swellable exterior coating is applied to the coated optical fiber so that it surrounds and contacts the secondary coating, but it may also be applied to any other layer of the fiber, such as the primary layer, or even a third, fourth, or fifth layer, etc., as long as the water-swellable exterior coating remains the outermost layer of the finished coated fiber.
  • the water-swellable exterior coating may be applied to the optical fiber as an outermost coating on top of the existing fiber optic coatings in the drawing process itself, or it may be applied in a subsequent operation. In an embodiment, the water-swellable coating is applied to the coated optical fiber in an operation independent from the fiber drawing process itself. If the water- swellable exterior coating is applied to the coated optical fiber in a subsequent operation, the coated optical fiber is often provided in a spool, with a portion of the fiber wound thereon.
  • the water-swellable exterior coating is applied to the optical fiber via a subsequent inking operation in an inking machine.
  • the optical fiber After the optical fiber has been provided, at least a portion thereof is subsequently fed into an inking machine.
  • the coated optical fiber is provided on a spool, the fiber will be unwound prior to being fed into the inking machine, in a method as is well-known in the art to which this invention applies.
  • the water-swellable coating may then be applied as a liquid composition to the surface of the section of coated optical fiber to form a coated optical fiber with a liquid water-swellable exterior coating.
  • the speed and thickness at which the water-swellable exterior coating is applied onto the coated optical fiber may be any suitable value. In an embodiment, the process is carried out at a speed of from 20 m/min to about lOOOm/min, or from about 50 m/min to about 500 m/min. In an embodiment, the water-swellable coating may be applied to the coated optical fiber at a thickness of 0.1 to less than 20 microns, or from 1 to 20 microns, or from 0.2 to 10 microns, or from 0.3 to 5 microns, or from 2 to 5 microns, or from 1 to 4 microns. Care should be taken to ensure that the thickness is applied as uniformly as is practically possible, in a manner well-known in the art.
  • the next step in the typical inking process involves exposing the coated optical fiber with the ink (or in the case of the present invention, the water-swellable exterior coating with or without an optional ink) to a light source capable of emitting ultraviolet radiation to affect curing of the liquid water-swellable exterior coating composition, in order to form a coated optical fiber with a cured water-swellable exterior coating.
  • a light source capable of emitting ultraviolet radiation to affect curing of the liquid water-swellable exterior coating composition
  • the light source is configured so as to impart an irradiance, at a surface of the liquid water-swellable exterior coating composition, or at least about 1 W/cm 2 ; more preferably from about 1 W/cm 2 to about 9 W/cm 2 , or from about 2 W/cm 2 to about 6 W/cm 2 , or from about 3 W/cm 2 to about 5 W/ cm 2 .
  • the coated optical fiber with the cured water-swellable exterior coating may then be rewound onto another spool to form a section of an at least partially rewound coated optical fiber.
  • the coating should be processed so as not to exhibit excessive tackiness, which will cause disparate adjoining sections of the coated fiber in the re-wound spool to stick together.
  • the coated optical fiber with the cured water-swellable exterior coating may alternatively be fed directly into the buffer tube during the extrusion process. This direct-feed approach may be useful if the water-swellable exterior coatings are too tacky and stick to each other during the winding process.
  • a fourth embodiment is a buffered bundle of optical fibers, comprising a flexible buffer tube possessing a length and a cavity over at least a portion of the length, and a plurality of coated optical fibers disposed within the cavity of the flexible buffer tube along the portion, wherein at least one of the plurality of coated optical fibers comprises a water-swellable exterior coating, further wherein said water-swellable exterior coating is configured to buckle and detach from the coated optical fiber at least one point along a section thereof within 3 minutes, or within 2 minutes, or within 10 seconds, or from 1 to 60 seconds, or from 10 seconds to 2 minutes, or from 3 seconds to 10 seconds from a time at which the cavity becomes filled with deionized water.
  • less than 100% of the optical fibers in the bundle are coated with a water-swellable exterior coating.
  • less than 90%, or less than 80%, or less than 70%, or less than 60%, or less than 50%, or less than 40%, or less than 30%, or less than 20%) of the optical fibers in the bundle are coated with a water-swellable exterior coating.
  • from 10% to 90%, or from 20% to 75%, or from 20% to 50%, or from 25% to 50% of the coated optical fibers comprise a water-swellable exterior coating.
  • each water-swellable exterior coating is configured for optimum detachability, integrity, and swellability
  • the amount of fibers which require such a water-swellable exterior coating in a given cable design to accomplish sufficient longitudinal water-blocking performance is dependent upon the total free volume in the buffer tube, which is influenced by the diameter of the buffer tube, the diameter of each individual coated optical fiber, the number of fibers in the tube, and the thickness of the water-swellable exterior coating, to name a few factors.
  • the buffered bundle of optical fibers possesses a quantity of water-swellable coating material which is configured to swell to fill less than 100% of the free volume in the buffered bundle, or less than 90% of the free volume, or less than 80%, or less than 70%.
  • the water-swellable coating material is configured to swell to fill at least 50%, or at least 60%, or at least 70%, or at least 80% of the free volume in the buffered bundle.
  • the utilization of the aforementioned exterior water-swellable coatings according to the present invention enables for more efficient "dry cable” designs than previous systems. That is in part due to the fact that the total volume of the water-swellable exterior coating material used is less than that of traditional yarns, tapes, and/or SAP-coated filaments, enabling for a maximum fiber density to be utilized, whilst maintaining or even improving longitudinal water-blocking
  • Table 1 describes the various components of the base composition used in all of the examples of Table 2.
  • a basic salt 50 wt.% NaOH solution from base composition of Table 1
  • the solution when used in a sequential step, may still possess slight amounts of solid particulate, however, this would not be expected to materially influence the homogeneity of the final solution.
  • a viscosity modifier for the base composition, a solution of 35% polyvinyl pyrrolidone with a number average molecular weight of approximately 160kDa in water was used was concentrated using a rotary evaporator to 50 wt.%.
  • the low viscosity base formulation (SAP-f) was made by adding a prescribed amount of acrylic acid (89 g acrylic acid was used in base composition), a monofunctional ethylenically unsaturated network former (138.7 g HPA in base composition), and water (22.6 g distilled water in base composition) in a 500 mL Erlenmeyer on a heating plate with temperature control in the solution. Subsequently, a prescribed amount of the basic salt solution (67.7g of the 50 wt.% NaOH solution per the base composition) was slowly added. During this process, precipitate initially formed and subsequently dissolved and the temperature increased, obviating the requirement to initially heat the solution. During the addition of the basic salt, the temperature was maintained between 50°C and 55°C. SAP-f was obtained after full addition of the basic salt solution and subsequent dissolution of any visibly-remaining precipitate.
  • composition/processing/construction type For each sample of selected composition/processing/construction type, multiple performance variables are reported below, including the composition's film water swelling ratio, and its buckling and detachability performance on fiber observed under microscope. Finally, each coating construction type was subjected to a longitudinal water blocking test. For each example, the overall result from the water blocking test was recorded. The results of each test are reported below in Table 2.
  • the tube 24 was connected via a needle and rubber tubing to a burette 21 (itself having a 1cm inner diameter) and filled with deionized water with a trace amount of dye 22 to a height 23 of 50 cm.
  • a burette 21 itself having a 1cm inner diameter
  • deionized water with a trace amount of dye 22 to a height 23 of 50 cm.
  • the valve 27 of the burette 21 was opened, allowing the water to flow into the fiber-filled tube 24. The water front could visually be observed to stop or progress over time.
  • a single SAP-coated fiber was placed on a slide under a microscope with 40x or lOOx magnification. Then, a droplet of deionized water was placed onto the fiber and the swelling of the SAP coating was observed under the microscope. Photographs were taken at specified intervals. The nature of the swelling and change in the SAP coating was then observed and reported in Table 2, with values recorded under the column headings "Buckle” and "Detachability.” It was observed that for a few samples, a phenomenon of disintegration occurred, meaning the coating resembles an almost fluid-like jelly and easily broke apart into many small pieces. Even if accompanied by a detachment, this is not a desired result.
  • a lOmil drawdown was provided, wherein such drawdown was cured by 3 passes of 1 J/cm 2 dose per pass under Fusion 600W/in D lamp on conveyor system with an irradiance of approximately 8 W/cm 2 as measured by an ILT490 radiometer.
  • a piece of the drawdown sample was cut to a square having a size of approximately 2cm x 2cm. Then, the sample was weighed to establish a dry weight. After this, the sample was then soaked in deionized water. After 30 minutes of soaking, the water was filtered out with a WypAll ® cleaning wipe. Then, the soaked sample was again weighed to provide a swelled weight.
  • the weight gain ratio was then calculated by determining the value of the swelled weight divided by the dry weight. Because it is known that the SAP film possesses a density which is similar to that of water, the volume swell ratio was approximated to be the same value as the calculated weight gain ratio and was recorded in the column headed by "Swell ratio" in Table 2.
  • compositions 12-24 were prepared in accordance with the general method described above with respect to the formulation of the base composition used in Table 1, albeit with the reagents and relative quantities differing, as is prescribed in Tables 3 and 4 below. The appearance of each coating was recorded, and the relative swell performance value was recorded under the row headed by "Swell Ratio," with such test performed in accordance with the film ratio swell test method described above. TABLE 3
  • Figs. 3a and 3b depict images of Example 5 from Table 2 at two different time intervals after water exposure.
  • Example 5 represents an example of a fiber which has buckled and detached after water immersion.
  • Fig. 3(a) provides a depiction approximately 3 seconds after the SAP- coated fiber had been immersed in water.
  • the SAP coating layer exhibited substantial buckling behavior, forming a pattern that closely resembles a high frequency periodic pattern along the axial direction with the peak of the buckles lifted away from the secondary coating.
  • the average distance between the peaks and valleys of the buckles was at least ⁇ . Beyond this, the SAP coating layer substantially detached from the secondary coating, with the buckles relaxed and the film fully swelled.
  • Fig. 3(b) This phenomenon is depicted in Fig. 3(b), which was a photograph taken at around 5 seconds after the water immersion.
  • Fig. 4 shows an example of an SAP-coated fiber that exhibits no buckling and no detaching from the coated fiber. It corresponds to Example 6 from Table 2.
  • This SAP coating layer showed a substantial thickness increase from its initial 3.5 ⁇ to approximately 41 ⁇ . Although the coating exhibited a slight wrinkling pattern, no portion of the film of the SAP layer lifted from the associated secondary coating, even an immersion period of 5 minutes. It did not reach the buckling threshold where the compressive axial force needs to overcome the critical buckling force.
  • FIG. 5 shows an example of a fiber that has buckled, but not detached, from its associated coated fiber after having reached its equilibrium swelling state.
  • This figure is a photograph of Example 9 from Table 2, wherein an SAP layer of ⁇ ⁇ was applied to a coated fiber. The swelling of the 1 micron SAP coating layer was effective in forming periodic buckles, however the buckles of the thin SAP coating layer were stable and did not further detach from fiber to enable the attainment of a relaxed, fully swelled state, as was depicted in Fig. 3(b).
  • Example 10 This enabled it to reach a fully swelled state, however it took a longer time to do so than Example 5.
  • the buckling stage lasted longer (to approximately 30 seconds); only enabling the coating of Example 10 to reach a fully detached and fully relaxed swelled stage after about 60 seconds.
  • This relative delay resulted in the inferior performance of Example 10 in the longitudinal water blocking test relative to that of Example 5, even though Example 5 possessed a thinner SAP coating layer.
  • Example 9 did not perform well in the water block test, but it is surmised that a reconfiguration of the composition used in accordance with some of the higher-swelling compositions of Table 3 could still yield passable results.
  • a first aspect of a first additional exemplary embodiment of the invention is a water- swellable, radiation curable coating composition for a fiber comprising:
  • the water-swellable, radiation curable coating composition for a fiber is a liquid at room temperature;
  • An additional aspect of the first additional exemplary embodiment is the water- swellable, radiation curable coating composition for a fiber of the previous aspect, wherein the acrylic acid is present in an amount, relative to the weight of the entire water-swellable, radiation curable coating composition for a fiber, of about 10 wt.% to about 50 wt.%, or about 10 wt.% to about 50 wt.%, or about 10 wt.% to about 30 wt.%, or about 10 wt.% to about 25 wt.%, or about 15 wt.% to about 40 wt.%, or about 18 wt. % to about 35 wt.%, or about 20 wt.% to about 30 wt.%.
  • An additional aspect of the first additional exemplary embodiment is the water- swellable, radiation curable coating composition for a fiber of any of the previous aspects, wherein the acrylic acid is present, in an amount relative to the entire composition, from about 0.14 to about 4.2 mol/kg, or from 0.7 to 2.1 mol/kg.
  • An additional aspect of the first additional exemplary embodiment is the water- swellable, radiation curable coating composition for a fiber of any of the previous aspects, wherein the acrylic acid salt is the reaction product of the acrylic acid and a basic salt.
  • An additional aspect of the first additional exemplary embodiment is the water- swellable, radiation curable coating composition for a fiber of any of the previous aspects, wherein the reaction of the acrylic acid and the basic salt neutralizes at least 10%-99% of the acrylic acid, or from at least 25% to about 95% of the acrylic acid, or from at least 33% to about 90% of the acrylic acid, or from at least 50% to about 90% of the acrylic acid, or at least 75% of the acrylic acid, or at least 90%) of the acrylic acid.
  • An additional aspect of the first additional exemplary embodiment is the water- swellable, radiation curable coating composition for a fiber of any of the previous aspects, wherein the composition comprises a ratio of the acrylic acid to the acrylic acid salt from about 12: 1 to about 1 : 12, or from about 6: 1 to about 1 :6, or from about 3 : 1 to about 1 : 1.
  • An additional aspect of the first additional exemplary embodiment is the water- swellable, radiation curable coating composition for a fiber of any of the previous aspects, wherein the basic salt is an alkali salt that further comprises a lithium, sodium, or potassium cation.
  • An additional aspect of the first additional exemplary embodiment is the water- swellable, radiation curable coating composition for a fiber of any of the previous aspects, wherein the acrylic acid salt comprises sodium acrylate.
  • An additional aspect of the first additional exemplary embodiment is the water- swellable, radiation curable coating composition for a fiber of any of the previous aspects, wherein the acrylic acid salt is present in an amount by weight, relative to the weight of the entire water- swellable, radiation curable coating composition for a fiber of about 1 wt.% to about 30 wt.%, more preferably from about 5 wt.% to about 15 wt.%.
  • An additional aspect of the first additional exemplary embodiment is the water- swellable, radiation curable coating composition for a fiber of any of the previous aspects, wherein the acrylic acid and/or acrylic acid salt is present in an amount, relative to the entire composition, from about 1.4 to about 8.3 mol/kg, or from 2.1 to 5.6 mol/kg, or from 2.5 to 4.9 mol/kg, or from, 2.8 to 4.2 mol/kg.
  • An additional aspect of the first additional exemplary embodiment is the water- swellable, radiation curable coating composition for a fiber of any of the previous aspects, wherein the molar ratio of the acrylic acid to the acrylic acid salt is less than or equal to 9: 1, or less than or equal to 3 : 1, or less than or equal to 1 : 1, or less than or equal to 1 : 3, or less than or equal to 1 : 10, or from 9: 1 to 1 : 10, or from 3 : 1 to 1 :3.
  • An additional aspect of the first additional exemplary embodiment is the water- swellable, radiation curable coating composition for a fiber of any of the previous aspects, wherein the monofunctional ethylenically unsaturated network former comprises an acrylate ester.
  • An additional aspect of the first additional exemplary embodiment is the water- swellable, radiation curable coating composition for a fiber of any of the previous aspects, wherein the ethylenically unsaturated network former comprises an acrylamide.
  • An additional aspect of the first additional exemplary embodiment is the water- swellable, radiation curable coating composition for a fiber of any of the previous aspects, wherein the monofunctional ethylenically unsaturated network former comprises a hydroxy functional acrylate compound.
  • An additional aspect of the first additional exemplary embodiment is the water- swellable, radiation curable coating composition for a fiber of any of the previous aspects, wherein the hydroxy functional acrylate compound comprises diethylene glycol ethyl ether acrylate, 2- hydroxypropyl acrylate, 3 -hydroxy propyl acrylate, hydroxy ethyl acrylate, 4 hydroxy butyl acrylate, 2,3-dihydroxy propyl acrylate, or 2-hydroxy-l-(hydroxymethyl)ethyl acrylate.
  • An additional aspect of the first additional exemplary embodiment is the water- swellable, radiation curable coating composition for a fiber of any of the previous aspects, wherein the monofunctional ethylenically unsaturated network former comprises an ethoxylated acrylate ether.
  • An additional aspect of the first additional exemplary embodiment is the water- swellable, radiation curable coating composition for a fiber of any of the previous aspects, wherein the ethoxylated acrylate ether comprises methoxy (polyethylene glycol) acrylate,
  • ethoxy(polyethylene glycol) acrylate ethylene glycol methyl ether acrylate, diethylene glycol methyl ether acrylate, triethylene glycol methyl ether acrylate, tetratethylene glycol methyl ether acrylate, ethylene glycol ethyl ether acrylate, diethylene glycol ethyl ether acrylate, triethylene glycol ethyl ether acrylate, tetratethylene glycol ethyl ether acrylate, or diethylene glycol -2- ethylhexyl ether acrylate.
  • An additional aspect of the first additional exemplary embodiment is the water- swellable, radiation curable coating composition for a fiber of any of the previous aspects, wherein the monofunctional ethylenically unsaturated network former is present in an amount by weight, relative to the weight of the entire water-swellable, radiation curable coating composition for a fiber of about 5 wt.% to about 50 wt.%, more preferably from about 10 wt.% to about 30 wt.%.
  • An additional aspect of the first additional exemplary embodiment is the water- swellable, radiation curable coating composition for a fiber of any of the previous aspects, wherein the monofunctional ethylenically unsaturated network former is present in an amount, relative to the entire composition, from about 0.38 to about 3.8 mol/kg, or from about 0.75 to about 2.3 mol/kg.
  • An additional aspect of the first additional exemplary embodiment is the water- swellable, radiation curable coating composition for a fiber of any of the previous aspects, wherein the photoinitiator comprises a phosphine oxide compound.
  • An additional aspect of the first additional exemplary embodiment is the water- swellable, radiation curable coating composition for a fiber of any of the previous aspects, wherein the photoinitiator is present in an amount by weight, relative to the weight of the entire water- swellable, radiation curable coating composition for a fiber of about 0.1 wt.% to about 5 wt.%, more preferably from about 0.2 wt.% to about 2 wt.%, or from about 0.5 wt.% to about 1.5 wt.%.
  • An additional aspect of the first additional exemplary embodiment is the water- swellable, radiation curable coating composition for a fiber of any of the previous aspects, wherein the viscosity modifier is water soluble.
  • An additional aspect of the first additional exemplary embodiment is the water- swellable, radiation curable coating composition for a fiber of any of the previous aspects, wherein the viscosity modifier comprises a polyvinyl alcohol, a polyvinyl pyrrolidone, a starch, a modified cellulose, a gelatin, a polyglycol compound, or a polyacrylic acid.
  • An additional aspect of the first additional exemplary embodiment is the water- swellable, radiation curable coating composition for a fiber of any of the previous aspects, wherein the modified cellulose comprises a methyl cellulose or hydroxyethyl cellulose compound.
  • An additional aspect of the first additional exemplary embodiment is the water- swellable, radiation curable coating composition for a fiber of any of the previous aspects, wherein the viscosity modifier comprises a polyvinyl pyrrolidone, wherein said polyvinyl pyrrolidone compound possess a number average molecular weight of 100 kDa to 500 kDa, or from 120 kDa to 200 kDa.
  • An additional aspect of the first additional exemplary embodiment is the water- swellable, radiation curable coating composition for a fiber of any of the previous aspects, wherein the viscosity modifier is present in an amount by weight, relative to the weight of the entire water- swellable, radiation curable coating composition for a fiber of about 5 wt.% to about 40 wt.%, or about 8 wt.%) to about 30 wt.%, or from about 10 wt.% to about 25 wt.%, or from about 15 wt.% to about 20 wt.%.
  • An additional aspect of the first additional exemplary embodiment is the water- swellable, radiation curable coating composition for a fiber of any of the previous aspects, wherein water is present, in an amount by weight, relative to the weight of the entire water-swellable, radiation curable coating composition for a fiber of about 3 wt.% to about 50 wt.%, or from about 5 wt.%) to about 45 wt.%, or from about 10 wt.% to about 40 wt.%, or from about 15 wt.% to about 35 wt.%.
  • An additional aspect of the first additional exemplary embodiment is the water- swellable, radiation curable coating composition for a fiber of any of the previous aspects, wherein the multifunctional crosslinker comprises a free-radically polymerizable compound with an average of greater than 1.9 functional groups.
  • An additional aspect of the first additional exemplary embodiment is the water- swellable, radiation curable coating composition for a fiber of any of the previous aspects, wherein the multifunctional crosslinker comprises a multifunctional acrylate or a multifunctional acrylamide.
  • An additional aspect of the first additional exemplary embodiment is the water- swellable, radiation curable coating composition for a fiber of any of the previous aspects, wherein the multifunctional crosslinker comprises a difunctional acrylate or trifunctional acrylate compound.
  • An additional aspect of the first additional exemplary embodiment is the water- swellable, radiation curable coating composition for a fiber of any of the previous aspects, wherein the multifunctional crosslinker comprises ethylene glycol diacrylate, diethylene glycol diacrylate, triethylene glycol diacrylate, tetra ethylene glycol diacrylate, ethoxylated hexane diol di acrylate, trimethylolpropane ethoxylate, methyl ether diacrylate, neopentyl glycol diacrylate, 1,3-butanediol diacrylate, glycerol-l,3-diglycerolate diacrylate, 1,6-hexanediyl bis[oxy-2-hydroxy-3, l- propanediyl] bis acrylate, pentaerythritol triacrylate, ethoxylated pentaerythritol triacrylate, 1,4, butanediol diacrylate or 1,6 hexane
  • An additional aspect of the first additional exemplary embodiment is the water- swellable, radiation curable coating composition for a fiber of any of the previous aspects, wherein the multifunctional crosslinker possesses a number average molecular weight from 200 to 20,000 g/mol, or preferably from 200 to 15,000 g/mol, or even more preferably from 400 to 10000 g/mol.
  • An additional aspect of the first additional exemplary embodiment is the water- swellable, radiation curable coating composition for a fiber of any of the previous aspects, wherein the multifunctional crosslinker comprises an ⁇ , ⁇ -methylene bisacrylamide compound or an n-n- ethylene bisacrylamide compound.
  • An additional aspect of the first additional exemplary embodiment is the water- swellable, radiation curable coating composition for a fiber of any of the previous aspects, wherein the multifunctional crosslinker is present, in an amount by weight, relative to the weight of the entire water-swellable, radiation curable coating composition for a fiber from greater than 0.1 wt.% to less than 20 wt.%, or from 0.1 wt.% to 15 wt.%, or from 0.1 wt.% to 10 wt.%, or from 0.1 wt.% to 5 wt.%), more preferably from about 0.5 wt.%> to about 3 wt.%>.
  • An additional aspect of the first additional exemplary embodiment is the water- swellable, radiation curable coating composition for a fiber of any of the previous aspects, wherein the multifunctional crosslinker is present in an amount, relative to the entire composition, from about 3.8 to about 190 mmol/ kg, or from about 19 to 110 mmol/kg.
  • An additional aspect of the first additional exemplary embodiment is the water- swellable, radiation curable coating composition for a fiber of any of the previous aspects, wherein the molar ratio of the acrylic acid and the acrylic acid salt to the monofunctional ethylenically unsaturated monomer is from about 1 : 1 to about 9: 1, or from about 1.05: 1 to about 6: 1, or from about 3 :2 to about 4: 1.
  • An additional aspect of the first additional exemplary embodiment is the water- swellable, radiation curable coating composition for a fiber of any of the previous aspects, wherein the molar ratio of the acrylic acid and the acrylic acid salt to the multifunctional crosslinker is from about 24: 1 to about 100,000: 1, or from about 32: 1 to about 1000: 1, or from about 50: 1 to about 200: 1.
  • An additional aspect of the first additional exemplary embodiment is the water- swellable, radiation curable coating composition for a fiber of any of the previous aspects, wherein the molar ratio of the monofunctional ethyl enically unsaturated network former to the
  • multifunctional crosslinker is from about 4: 1 to about 1000: 1, or from about 9: 1 to about 200: 1, or from about 20: 1 to about 100: 1.
  • An additional aspect of the first additional exemplary embodiment is the water- swellable, radiation curable coating composition for a fiber of any of the previous aspects, wherein the composition further comprises an ink.
  • An additional aspect of the first additional exemplary embodiment is the water- swellable, radiation curable coating composition for a fiber of the previous aspect, wherein the ink comprises a dye or pigment.
  • An additional aspect of the first additional exemplary embodiment is the water- swellable, radiation curable coating composition for a fiber of either of the two previous aspects, wherein the ink is present in an amount, relative to the weight of the entire water-swellable, radiation curable coating composition for a fiber of about 0.01 wt.% to about 5 wt.%, or from about 0.05 wt.%) to about 2 wt.%, or from about 0.1 wt.%> to about 1 wt.%>.
  • An additional aspect of the first additional exemplary embodiment is the water- swellable, radiation curable coating composition for a fiber of any of the previous aspects, wherein the composition is substantially free from a component derived from, or possessing acyl groups derived from, a methacrylic acid.
  • An additional aspect of the first additional exemplary embodiment is the water- swellable, radiation curable coating composition for a fiber of any of the previous aspects, wherein the composition possesses less than 3%, or less than 2%, or less than 1%, or less than 0.5%, or less than 0.1%) of a component derived from a methacrylic acid.
  • An additional aspect of the first additional exemplary embodiment is the water- swellable, radiation curable coating composition for a fiber of any of the previous aspects, wherein the component derived from a methacrylic acid includes a methacrylate, a methacrylate ester, or a methacrylamide.
  • An additional aspect of the first additional exemplary embodiment is the water- swellable, radiation curable coating composition for a fiber of any of the previous aspects, wherein the composition possesses a plurality of free-radically polymerizable monomers, wherein the free- radically polymerizable monomers consist essentially of components derived from acrylic acid.
  • An additional aspect of the first additional exemplary embodiment is the water- swellable, radiation curable coating composition for a fiber of any of the previous aspects, wherein the composition further comprises an additive.
  • An additional aspect of the first additional exemplary embodiment is the water- swellable, radiation curable coating composition for a fiber of any of the previous aspects, wherein the water-swell able radiation curable coating composition for a fiber possesses a viscosity of from 700 to 2500 cPs at 25°C.
  • An additional aspect of the first additional exemplary embodiment is the water- swellable, radiation curable coating composition for a fiber of any of the previous aspects, wherein the water-swell able, radiation curable coating possesses, when coated as a 10 mil drawdown film on a glass plate, a swell ratio of at least 5x, or at least lOx, or at least 20x, or at least 30x, or at least 40x, and less than 300x, or less than 200x, or less than lOOx.
  • An additional aspect of the first additional exemplary embodiment is the water- swellable, radiation curable coating composition for a fiber of any of the previous aspects, wherein when the coating is applied at a thickness of about 3 microns to a 4-meter section of an optical fiber possessing a diameter of about 245 microns, and inserted into a horizontally-disposed tube possessing an inner diameter of about 1mm and exposed at a first end to deionized water that is gravity-fed by a 0.5m vertical water column for 10 seconds, a travel of said deionized water does not extend beyond 3 meters along the length of the water-impermeable tube from the first end.
  • An additional aspect of the first additional exemplary embodiment is the water- swellable, radiation curable coating composition for a fiber of any of the previous aspects, wherein the composition is substantially free from a methacrylate compound.
  • An additional aspect of the first additional exemplary embodiment is the water- swellable, radiation curable coating composition for a fiber of any of the previous aspects, wherein the composition is substantially free from a compound which possesses acyl groups derived from methacrylic acid.
  • An additional aspect of the first additional exemplary embodiment is the water- swellable, radiation curable coating composition for a fiber of any of the previous aspects, wherein the composition possesses, relative to the weight of the entire composition, less than 3 wt.%, or less than 2 wt.%, or less than 1 wt.%, or less than 0.5 wt.% of a methacrylate compound.
  • An additional aspect of the first additional exemplary embodiment is the water- swellable, radiation curable coating composition for a fiber of any of the previous aspects, wherein the composition possesses, relative to the weight of the entire composition, less than 3 wt.%, or less than 2 wt.%, or less than 1 wt.%, or less than 0.5 wt.% of a compound which possesses acyl groups derived from methacrylic acid.
  • An additional aspect of the first additional exemplary embodiment is the water- swellable, radiation curable coating composition for a fiber of any of the previous aspects, wherein the composition comprises one or more compounds possessing free-radically polymerizable functional groups, wherein the free-radically polymerizable groups consist essentially of acrylate functional groups.
  • a first aspect of a second additional exemplary embodiment of the invention is a coated optical fiber comprising:
  • water-swellable exterior coating is configured to buckle and detach from the secondary coating at least one point along a section of the coated optical fiber within 3 minutes after the coated optical fiber has been submerged in deionized water within 10 seconds, or within 2 minutes.
  • An additional aspect of the second additional exemplary embodiment is the coated optical fiber of the previous aspect, wherein the water-swellable exterior coating possesses a thickness of from 0.1 to less than 20 microns, or from 0.2 to 10 microns, or from 0.3 to 5 microns, or from 1 to 4 microns, or from 2 to 20 microns, or from 2 to 15 microns, or from 2 to 10 microns, or from 2 to 8 microns, or from 2 to 5 microns.
  • An additional aspect of the second additional exemplary embodiment is the coated optical fiber of any of the previous aspects, wherein when a 4 meter section of the coated optical fiber is inserted into a horizontally-disposed water-impermeable tube possessing an inner diameter of about 1mm and exposed at a first end to deionized water that is gravity-fed by a 0.5m vertical water column for 10 seconds, a travel of said deionized water does not extend beyond 3 meters along the length of the water-impermeable tube from the first end.
  • An additional aspect of the second additional exemplary embodiment is the coated optical fiber of any of the previous aspects, wherein when a continuous section of five coated optical fibers are inserted into a horizontally-disposed water-impermeable tube possessing an inner diameter of about 1mm and a and exposed at a first end to deionized water that is gravity-fed by a 0.5m vertical water column for 10 seconds, a travel of said deionized water does not extend beyond 3 meters along the length of the water-impermeable tube from the first end.
  • An additional aspect of the second additional exemplary embodiment is the coated optical fiber of any of the previous aspects, wherein the water-swellable exterior coating is the cured product of the water-swellable radiation curable coating of any of the aspects of the first additional exemplary embodiment.
  • An additional aspect of the second additional exemplary embodiment is the coated optical fiber of any of the previous aspects, wherein the water-swellable exterior coating is further configured to possess a three-dimensional swelling ratio of from about 3x to about 300x, or from about 5x to about 250x, or from about 30x to about 200x.
  • An additional aspect of the second additional exemplary embodiment is the coated optical fiber of any of the previous aspects, wherein the water-swellable exterior coating possesses a top surface percent reacted acrylate unsaturation (%RAU) of at least 80%, more preferably at least 90%, or at least 95%, or at least 98%, or at least 99% when tested according to an FTIR method.
  • %RAU top surface percent reacted acrylate unsaturation
  • a first aspect of a third additional exemplary embodiment of the invention is a method of applying a liquid water-swellable coating to a coated optical fiber comprising the steps of:
  • water-swellable exterior coating is configured to buckle and detach from the coated optical fiber at least one point along the section of the coated optical fiber within 3 minutes after the time from which the coated optical fiber with the water-swellable exterior coating has been submerged in deionized water.
  • An additional aspect of the third additional exemplary embodiment is the method according to the preceding aspect, wherein the wherein the liquid water-swellable coating composition is defined by the composition of any of aspects of the first additional exemplary embodiment.
  • An additional aspect of the third additional exemplary embodiment is the method according to any of the preceding aspects, wherein the providing step comprises unwinding the section of coated optical fiber from a first spool.
  • An additional aspect of the third additional exemplary embodiment is the method according to any of the preceding aspects, wherein the providing step comprises feeding the section of the coated optical fiber into an inking machine.
  • An additional aspect of the third additional exemplary embodiment is the method according to any of the preceding aspects, wherein the liquid water-swellable coating composition is applied to the exterior surface of the section of the coated optical fiber at a thickness of from 0.1 to 20 microns, or from about 0.2 to about 10 microns, or from about 0.3 to about 5 microns, or from about 1 to about 4 microns.
  • An additional aspect of the third additional exemplary embodiment is the method according to any of the preceding aspects, wherein the liquid water-swellable coating composition possesses a viscosity of from 700 to 2500 cPs at 25°C.
  • An additional aspect of the third additional exemplary embodiment is the method according to any of the preceding aspects, further comprising the step of re-winding at least a portion of the coated optical fiber with the cured water-swellable exterior coating onto a second spool to form a section of partially rewound coated optical fiber.
  • An additional aspect of the third additional exemplary embodiment is the method according to any of the preceding aspects, further comprising the step of feeding the coated optical fiber with the water-swellable exterior coating directly into a buffer tube in a buffer tube extrusion process.
  • An additional aspect of the third additional exemplary embodiment is the method according to any of the preceding aspects, wherein the water-swellable exterior coating possesses a top surface percent reacted acrylate unsaturation (%RAU) of at least 80%, more preferably at least 90%), or at least 95%, or at least 98%>, or at least 99% when tested according to an FTIR method.
  • %RAU top surface percent reacted acrylate unsaturation
  • An additional aspect of the third additional exemplary embodiment is the method according to any of the preceding aspects, wherein the winding of the coated optical fiber occurs at a speed of from 20 m/min to about lOOOm/min, or from about 50 m/min to about 500 m/min.
  • An additional aspect of the third additional exemplary embodiment is the method according to any of the preceding aspects, wherein the light source is configured to impart an irradiance, at a surface of the liquid water-swellable exterior coating, or at least about 1 W/cm 2 ; more preferably from about 1 W/cm 2 to about 9 W/cm 2 , or from about 2 W/cm 2 to about 6 W/cm 2 , or from about 3 W/cm 2 to about 5 W/ cm 2 .
  • An additional aspect of the third additional exemplary embodiment is the method according to any of the preceding aspects, wherein the water-swellable exterior coating is further configured to possess a three-dimensional swelling ratio of from about 3x to about 300x, or from about 5x to about 250x, or from about 30x to about 200x.
  • a first aspect of a fourth additional exemplary embodiment of the invention is a buffered bundle of optical fibers, comprising
  • a flexible buffer tube possessing a length and a cavity over at least a portion of the length
  • At least one of the plurality of coated optical fibers comprises a water-swellable exterior coating; wherein said water-swellable exterior coating is configured to buckle and detach from the coated optical fiber at least one point along a section thereof within 3 minutes from a time at which the cavity becomes filled with deionized water.
  • An additional aspect of the fourth additional exemplary embodiment is the buffered bundle of optical fibers of the preceding aspect, wherein the water-swellable exterior coating is the cured product of a composition as defined by any of the aspects of the first additional exemplary embodiment of the invention.
  • An additional aspect of the fourth additional exemplary embodiment is the buffered bundle of optical fibers of any of the preceding aspects, wherein at least two coated optical fibers comprise a water- swell able exterior coating.
  • An additional aspect of the fourth additional exemplary embodiment is the buffered bundle of optical fibers of any of the preceding aspects, wherein at least one of said water-swellable exterior coatings possesses a three-dimensional swelling ratio of from about 3x to about 300x, or from about 5x to about 250x, or from about 30x to about 200x.
  • An additional aspect of the fourth additional exemplary embodiment is the buffered bundle of optical fibers of any of the preceding aspects, wherein at least one of said water-swellable exterior coatings possesses a thickness of from 0.1 to less than 20 microns, or from about 0.2 to about 10 microns, or from about 0.3 to about 5 microns, or from about 1 to about 4 microns.
  • An additional aspect of the fourth additional exemplary embodiment is the buffered bundle of optical fibers of any of the preceding aspects, wherein at least one of said water-swellable exterior coating possesses a top surface percent reacted acrylate unsaturation (%RAU) of at least 80%, more preferably at least 90%, or at least 95%, or at least 98%, or at least 99% when tested according to an FTIR method.
  • %RAU top surface percent reacted acrylate unsaturation
  • An additional aspect of the fourth additional exemplary embodiment is the buffered bundle of optical fibers of any of the preceding aspects, further comprising a free volume which is defined by a volume of the cavity over a portion of the length minus the volume of the plurality of coated optical fibers disposed therein along said portion, and a total amount of water-swellable exterior coating, wherein the total amount of water-swellable exterior coating is configured to swell to less than 100% of the free volume, or between 50%-90% of the free volume, or between 60%- 90% of the free volume, or between 70%-90% of the free volume, or between 50%-80% of the free volume, or between 50%-70% of the free volume.
  • An additional aspect of the fourth additional exemplary embodiment is the buffered bundle of optical fibers of any of the preceding aspects, wherein at least 25% of the coated optical fibers possess a water-swellable exterior coating.
  • An additional aspect of the fourth additional exemplary embodiment is the buffered bundle of optical fibers of any of the preceding aspects, wherein from 25% to 90%, or 25% to 75%, or 25%) to 50% of the coated optical fibers comprise a water-swellable exterior coating.
  • An additional aspect of the fourth additional exemplary embodiment is the buffered bundle of optical fibers of any of the preceding aspects, wherein the buffered bundle, when placed horizontally and exposed at a first end to deionized water that is gravity-fed by a 0.5m vertical water column for 5 minutes, prevents the travel of said deionized water beyond 3 meters along the length of the buffered bundle from the first end.
  • wt. % means the amount by mass of a particular constituent relative to the entire liquid radiation curable composition into which it is incorporated.

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EP18807797.8A 2017-11-03 2018-11-05 Wasserblockierende systeme mit fasern, die mit flüssigen, strahlungshärtbaren harzzusammensetzungen beschichtet sind Pending EP3687949A1 (de)

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